The treatment of injuries to the spine includes the use of elongated rigid plates in the stabilization of the spine. Plating designs may allow for a uni-cortically or bi-cortically intrinsically stable implant. It has also been found that the plates can be useful in stabilizing the upper or lower cervical, thoracic, lumbar and/or sacral spine in traumatic, degenerative, tumorous or infectious processes. Moreover, these plates provide the additional benefit of allowing simultaneous neural decompression with immediate stability.
During the many years of development of spinal plating systems various needs have been recognized. For instance, the plate should provide stabilization that can control movement of each vertebral motion segment in six degrees of freedom and withstand axial loading of the spine. The plate should also be able to maintain stress levels below the endurance limits of the material while also providing a thickness that is small to lower its protrusion into the adjacent tissue along the spine. The anchors employed to connect the plate to the vertebrae should not loosen over time or back out from the plate. Many spinal plating systems have been developed in the last couple of decades that address some of the needs and requirements for spinal stabilization. Examples include those disclosed in U.S. Pat. No. 6,152,927 and U.S. Patent Application Publication No. 2004/0215195, each of which is incorporated herein by reference in its entirety.
Plates made to provide a non-rigid stabilization construct are beneficial in that the plate can have a lower modulus as compared to plates that are made rigidly. Non-rigid stabilization constructs can also be made from non-metal materials and provide desirable imaging characteristics since certain metals can produce imaging artifacts and scatter, which hinder the inspection of bone growth when using conventional imaging via X-ray, CAT scanning, or MRI techniques. However, non-rigid plates should also be adapted to allow secure engagement of the bone anchors to the bone to secure the plate along the spinal column. Non-rigid plates can be damaged during installation by bone anchors passing through the plate holes, or by the bone anchors or any anchor retention devices deforming the plate when engaged to the plate. Furthermore, bone anchors and anchor retaining devices may be susceptible to loosening or backing out after engagement with the plate.